For recently discontinued models (1–5 years old), these retailers offer professional testing and warranties. Back Market
The best places to buy "old" Apple products depend on whether you are looking for (like a 2-year-old iPhone) or vintage/collector items (like a 1990s Macintosh). Refurbished Modern Products where to buy old apple products
If you cannot connect to the servers, check if you have some antivirus or firewall blocking the connection.